1.3- Butadiene 2-chloro-3-methyl

Oxidative cleavage of the complex 549 with CuCri affords 2,3-bis(chloro-methyl)-1,3-butadiene (550) and regenerates PdCri. Thus the preparation of this interesting dimerization product 550 can be carried out with a catalytic amount of PdCl2 and two equivalents of CuCb in MeCN[495], Similarly, treatment of allene with PdBr2 affords the dimeric complex 551. Treatment of this complex with 2 equiv, of bromine yields the dibromide 552. The tetra-bromide 553 is obtained by the reaction of an excess of bromine[496]. Similarly,... 

A,iV-diaryl-l,4-diaza-l,3-butadienes also form stable dimethyl- and chloro(methyl)-platinum complexes 16 and 17. Addition of the ligand to Pt2Me4(/i-SMe2)2 and PtMe2(cod) yields the dimethylplatinum(ii) complexes having chelating diimines. 

CH2 CH C CH. Colourless gas with a sweet odour b.p. 5°C. Manufactured by the controlled low-temperature telomerization of ethyne in the presence of an aqueous solution of CuCI and NH Cl. Reduced by hydrogen to butadiene and, finally, butane. Reacts with water in the presence of HgSO to give methyl vinyl ketone. Forms salts. Forms 2-chloro-butadiene (chloroprene) with hydrochloric acid and certain metallic chlorides. 

Simple conjugated dienes used in polymer synthesis include 1,3-butadiene, chloroprene (Z-chloro-l -butadiene), and isoprene (2-methyl-l,3-butadiene). Isoprene has been prepared industrially by several methods, including the acid-catalyzed double dehydration of S-methyl-l/S-butanediol. 

The synthesis of 2-chloro-2,3,3-trifluorocyclobutyl acetate illustrates a general method of preparing cyclobutanes by heating chlorotrifluoroethylene, tetrafluoroethylene, and other highly fluorinated ethylenes with alkenes. The reaction has recently been reviewed.11 Chlorotrifluoroethylene has been shown to form cyclobutanes in this way with acrylonitrile,6 vinylidene chloride,3 phenylacetylene,7 and methyl propiolate.3 A far greater number of cyclobutanes have been prepared from tetrafluoroethylene and alkenes 4,11 when tetrafluoroethylene is used, care must be exercised because of the danger of explosion. The fluorinated cyclobutanes can be converted to a variety of cyclobutanes, cyclobutenes, and butadienes. 

Polarization is found in reactions involving chlorides. 1,1-Dichloro-2,2-dimethylcyclopropane (26) reacts with lithium ethyl in benzene-ether solution (40°) giving mainly l-chloro-2,2-dimethylcyclopropane (27 X = H) and 3-methyl-l,2-butadiene (28) both of which are polarized (Ward et al., 1968). If n- or t-butyl lithium are used in the reaction, the butene produced by disproportionation shows only net polarization. 

The electrophilic addition of nitrosyl chloride with 3-methyl-l,2-butadiene at 0°C afforded 2-nitroso-3-chloro-3-methyl-l-butene, in which the nitrosyl group was connected to the central carbon atom [10]. 

Dichlorination of tetramethylallene afforded 3-chloro-2,4-dimethyl-l,3-pentadiene as the single product, whereas the same reaction of 1,1-dimethylallene yielded a mixture of 2-chloro-3-methyl-l,3-butadiene, 2,3-dichloro-3-methyl-l-butene and 1,2-dichloro-3-methyl-2-butene, indicating the intermediacy of the 2-chloroallylic cationic intermediate 11 [13]. 

Monomers which can add to their own radicals are capable of copolymerizing with SO2 to give products of variable composition. These include styrene and ring-substituted styrenes (but not a-methylstyrene), vinyl acetate, vinyl bromide, vinyl chloride, and vinyl floride, acrylamide (but not N-substituted acrylamides) and allyl esters. Methyl methacrylate, acrylic acid, acrylates, and acrylonitrile do not copolymerize and in fact can be homopolymer-ized in SO2 as solvent. Dienes such as butadiene and 2-chloro-butadiene do copolymerize, and we will be concerned with the latter cortpound in this discussion. 

Natural rubber (Hevea brasiliensis) is as-poly-2-methyl-1,4-butadiene, and gutta-percha (Palaquium oblongi/olium) and balata (Minusops globosa) are polymers of isoprene (2-methyl-1,4-butadiene) with trans configurations. Neoprene is a polymer of 2-chloro-1,3-butadiene (chloroprene). 

Methyl-l, 2-butadiene, 6 JV-Methyl-JV -/-butyldiazine N -oxide, 349 Methyl carbamate, 238 Ar-Methyl-m-chloro-p-nitrosoaniline, 391 Methyl chlorosulfinate, 75... 

When l-chloro-3-methyl-l,2-butadiene is allowed to stand for several days with the catalyst above, it is converted to 4-chloro-2-methyl-1,3-butadiene [58] (Eq. 46). 

The more important dienes for the manufacture of synthetic rubbers are 1,3-butadiene, 2-chloro-1,3-butadiene (chloroprene), and 2-methyl-1,3-butadiene (isoprene) ... 

FIG. 18.3 Activation energy of diffusion as a function of Tg for 21 different polymers from low to high temperatures, ( ) odd numbers (O) even numbers 1. Silicone rubber 2. Butadiene rubber 3. Hydropol (hydrogenated polybutadiene = amorphous polyethylene) 4. Styrene/butadiene rubber 5. Natural rubber 6. Butadiene/acrylonitrile rubber (80/20) 7. Butyl rubber 8. Ethylene/propylene rubber 9. Chloro-prene rubber (neoprene) 10. Poly(oxy methylene) 11. Butadiene/acrylonitrile rubber (60/40) 12. Polypropylene 13. Methyl rubber 14. Poly(viny[ acetate) 15. Nylon-11 16. Poly(ethyl methacrylate) 17. Polyethylene terephthalate) 18. Poly(vinyl chloride) 19. Polystyrene 20. Poly (bisphenol A carbonate) 21. Poly(2,6 dimethyl-p.phenylene oxide). 

The preparation of 2-chlorothiopyrylium salts can be accomplished by a two-component synthesis. Reaction of /ru/ij-rra/i5-1,4-diphenyl-1,3-butadiene with excess thiophosgene gives 2-chloro-3,6-diphenylthiopyry-lium chloride 102 in high yield (Scheme 7) (67ZC227). The reaction probably consists in a Diels-Alder cycloaddition, followed by elimination of HCl and hydride abstraction. When the reaction was carried out with l-phenyl-3-methyl-l,3-butadiene, the 3,5-disubstituted thiopyrylium 103 was isolated without evidence of the 4,6-disubstituted regioisomer (84AP938). 

Butadiene 4-Chloro-3-(chloro-difluoro-methyl)-l, 4,4-trifluoro-E10 (OH F In - 1,2-Dien)... 

CHs)jC(OH)C = CH, with hydrochloric acid, extensive production of 2-chloro-3-methyl-1,3-butadiene, HiC = C(CH5)C(Cl)=CHj, occurs instead of the expected metathesis product. w-Methoxybenzyl alcohol has been converted to the corresponding halide in 90% yield without... 

The bicyclo[4.2.0]octane approach has proved valuable in particular situations. South and Liebe-skind have converted the adduct obtained from 3-methyl-1-trimethylsilyloxy-1,3-butadiene and 1,4-di-chloro-3,3,4-trifluorocyclobutene into 3-hydroxy-5-methylbenzocyclobutene-l,2-dione in 72% yield. ... 

When the cyclobutene ring is transformed into a butadiene, the C-3—C-4 bond breaks. As it does so, there is rotation about the C-1—C-4 bond and the C-2—C-3 bond, so that the substituents on the breaking C-3—C-4 a bond rotate into the plane of the conjugated diene system of the product. In the starting cyclobutene, the methyl and chloro groups lie above the plane of the four ring carbons in the product, these groups lie in the same plane as the four carbon atoms of the butadiene. If all possible rotations about the C-3—C-4 a- bond were allowed, four different products would be formed, two by conrotatory processes and two by disrotatory processes. We will take a closer look at this process. 

C5H7CI 1 -chloro-3-methyl 1,3-butadiene 51034-46-9 373.85 31.908 1,2 4725 C5H7N302 2-amino-4,6-dihydroxy-5-methylpyrimidine 55477-35-5 344.45 29.165 2... 

PCIRuC.wH24. Ruthenium(II), chloro(T -hexamethylbenzene)hydrido(tri-phenylphosphine)-, 26 181 PCIiCiiHn, Phosphonous dichloride, (2,4,6-tri-tm-butylphenyl)-, 27 236 PCIjSiiCioHjT, Phosphonous dichloride, (tris(trimethylsilyl)methyl]-, 27 239 PCoC Hjo, Cobalt, (-ri -cyclopentadienyl)-(n -1, l -( 1,2-ethynediyl)bisbenzene]-(triphenylphosphine)-, 26 192 PCoCjiHm, Cobalt, (ii -cyclopentadienyl)-(2,3-dimethyl-1,4-diphenyl-l, 3-butadiene- 1,4-diy l)(tripheny Iphosphine)-, 26 195... 

Problem 8.10 Account for the fact that 2>methyM,3-butadiene reacts (a) with HCI to yield only 3-chloro-3-mcthyl-l-butcne and l-chloro-3-methyl-2-butene ... 

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